1. Field of the Invention
The present invention relates to reclaiming of elastomers. More particularly, the present invention relates to compositions containing elastomeric particles and methods for producing the compositions.
2. Description of Related Art
Various types of elastomeric materials (e.g., natural rubber, synthetic rubber, recycled rubbers containing polyethylene and/or polypropylene, vulcanized rubber, carbon black, waste from tire production, various polymers, various plastics, thermoplastic elastomers, thermoplastic vulcanates and polyethylene plastics) can be recycled or reclaimed, and used to make other products. For example, synthetic rubber obtained form used vehicle tires can be used in a process to make asphalt. In recycling and reusing such elastomeric materials, it is often necessary to reduce the particle size of the elastomeric materials. The relatively small particles are typically more susceptible to chemical modification, and mechanically easier to blend with other components.
One method for producing elastomeric materials with a reduced particle size include milling the elastomer between horizontal grinding stones in a horizontal grinding mill. Similar milling techniques have been developed and used in the flour, paper pulp industry and the paint pigment-compounding industries. A horizontal grinding mill includes opposite milling wheels with a fixed wheel (stone) and the other wheel rotates relative to the fixed wheel. To grind elastomeric materials a composition containing the elastomer is directed to an area between the two stones, and is ground to a fine state. However, such known milling methods have the disadvantage of creating friction, which can increase the temperature of the composition. Increased composition temperatures can cause xe2x80x9cflash overxe2x80x9d in which the composition becomes a largely dry elastomeric mass that inhibits further grinding. In the case of rubber, e.g., synthetic rubber, these milling methods often do not produce a uniformly fine rubber powder that passes through a minus 50-mesh.
Accordingly, there is an interest to improve upon current methods for making elastomeric materials of a relatively small particle size. The advantages sought include decreasing the amount of soak time, or decreasing the time it takes to bring the elastomer to the desired particle size. There is also interest to convert an elastomer to a decreased particle size at relatively low process temperatures to minimize flash over. There is also interest for elastomeric compositions that are more susceptible to chemical modification such that their physical properties can also be modified. The present invention addresses one or more of these desired process parameters in making novel elastomeric compositions for later use in other products.
Reclaimed elastomeric materials are often used in downstream products such as construction materials, e.g., asphalt and roofing products. In asphalt production, reclaimed or recycled rubber is added to the asphalt mixture in stages and at a different temperatures than virgin rubbers and unvulcanized materials. As a result, if an asphalt manufacturer desires to add block rubber such as SBS, virgin rubber or wide spec rubber, into the asphalt as well as a recycled rubber, the block material is generally added in a first asphalt tank at a temperature of about 380xc2x0 F. The coursely ground reclaimed material is typically added in a separate asphalt tank at a higher temperature of about 410xc2x0 F. This methodology is cumbersome and requires may process steps and temperature controls. To avoid the need of having to purchase and maintain additional process equipment many asphalt produces tend not to include recycled materials.
The invention is directed to a method of making a slurry with reclaimed elastomer, the method comprising providing a milling composition, wherein the milling composition comprises an elastomer, a wetting agent, and a devulcanizing effective amount of an aromatic alcohol, and grinding the milling composition. The aromatic alcohol is selected from the group consisting of phenol and creosol. The aromatic alcohol can be drived from anise seed or birch bark, which is ground with the elastomer.
The invention is also directed to a composition comprising: ground reclaimed elastomeric particles; a wetting agent; and a devulcanizing effective amount of an aromatic alcohol selected from the group consisting of phenol and creosol, The aromatic alcohol can be drived from anise seed or birch bark, which is ground with the elastomer. The wetting agent is preferably pyrrolidone or a pyrrolidone derivative.
The invention is also directed to an asphalt composition comprising elastomeric particles that were reduced in particle size in the presence of a wetting agent and a devulcanizing amount of an aromatic alcohol selected from the group consisting of phenol and creosol. The asphalt composition can also contain a fibrous material selected from ground anise seeds, ground birch bark, or a mixture thereof.